Heat exchanger made of an aluminum alloy

Abstract

There is disclosed a heat exchanger made of an aluminum alloy having a radiator part (10) and an oil cooler part (11) in combination and manufactured integrally by the brazing method, wherein a refrigerant tank (13) for covering and sealing the oil cooler part is made of an aluminum alloy, an aluminum alloy containing Si in an amount from more than 7.0 wt % to 12.0 wt %, Fe in an amount from more than 0.05 wt % to 0.5 wt %, Cu in an amount from more than 0.4 wt % to 8.0 wt %, Zn in an amount from more than 0.5 wt % to 10.0 wt %, and the balance of aluminum and inevitable impurities is used as a filler material of brazing sheets that are used for the oil cooler part and are brazed in the tank, and the refrigerant tank is assembled integrally with the radiator part and the oil cooler part by brazing with the brazing material. The heat exchanger made of an aluminum alloy by using an aluminum material instead of a resin tank, can be easily recycled, is excellent in corrosion resistance, and can be manufactured without requiring a step of caulking a tank.

Description

The present invention relates to a heat exchanger made of an aluminum alloy, and more particularly to a heat exchanger with a radiator and an oil cooler integrated that is produced by using aluminum alloy brazing sheets.A heat exchanger having a radiator and an oil cooler in combination is manufactured by assembling a radiator core part (10) and an oil cooler part (11) (oil passages (7) formed by joining brazing sheets (8) are illustrated in a simplified manner in the drawings) and then mechanically associating them with tanks (6), for example, as shown perspectively in FIG. 4.Herein, as is apparent from FIG. 5 showing a perspective view, the radiator is made up of the radiator core part (10), comprising flat tubes (3), thin fins (1), side supports (12), and headers (4), and the tanks (6). Each of the corrugated thin fins (1) is formed between the flat tubes (3), with the corrugated thin fin integrated with the flat tubes, and the ends of the flat tubes (3) are open to space (2) for...

AI Technical Summary

Benefits of technology

In and Sn make the electric potential of the filler material base to improve the corrosion resistance of the members constituting refrigerant passages. In and Sn are added to assist the effect of Zn. If its amount is 0.002 wt % or less, its effect is not satisfactory whereas if its amount is over 0.3 wt %, the workability in rolling of the alloy is lowered.

The addition of Ga and / or Ge is effective to make base the potential of the filler material and hence to improve the corrosion resistance of a refrigerant passage component by such a sacrifice anode effect. The addition of Ga and / or Ge also functions to reduce the potential of the filler material containing Cu to a value close to the potential of a core alloy, and hence to improve the corrosion resistance. Ga and / or Ge can be added to assist the additional effect of Zn, In and / or Sn, or in place of them. When the amount of Ga is more than 1.0 wt % or the amount of Ge is more than 2.0 wt %, the self-corrosion resistance of the filler material is reduced, which may degrade the workability in rolling of the alloy.

Li, Na, K, Ca, Ba, Sr, Be, and Bi are effective to improve the flowability, that is, the brazing properties of the Al alloy filler material by forming a brittle oxide or a low melting point compound on the surface of the filler material to facilitate the breakage of the oxide film. When the amount of Li is more than 1.0 wt %, that of Bi is more than 0.5 wt %, or that of Na, K, Ca, Sr, Ba and Be is more than 0.2 wt % respectively, the workability in rolling of the alloy may be degraded.

Mn, Ni, Cr, Ti, Zr, and V function to form an intermetallic compound upon solidification of the filler material after being melted and hence to increase the strength of a brazing portion. When the amount of Mn is 0.05 wt % or less, the additional effect may be insufficient, while when the amount of Mn is more than 1.2 wt %, that of Ni is more than 0.6 wt %, or that of Cr, Ti, Zr and V is more than 0.2 wt % respectively, the workability in rolling of the Al alloy may be degraded.

Problems solved by technology

However, conventionally the tank (6) is generally made of a resin material, and the tank (6) has to be attached in a step separated from the step of assembling the radiator part and the oil cooler part by brazing, so that there is a difficulty that additional step is required.

Further, in such a heat exchanger, the part between the resin tank (6) and the header (4) that is fastened, is required to be caulked through a resin packing (5) or the like, which leads to a defect that crevice corrosion is apt to take place at the boundary between the resin packing (5) and the header (4).

However, as shown in FIG. 4, when the heat exchanger has, as the tank (6), a tank made of resin, the resin tank has to be removed purposely when the automobile is disassembled, and that becomes a bottleneck in the recycling process.

Therefore, if the brazing of the oil cooler is incomplete, it cannot be repaired anymore.

Thus, it is required that the brazing be effected completely, but it is conventionally difficult due to the following reason.

Since the oil cooler part is covered with the tank, the temperature of the brazing is not elevated satisfactorily, and defective brazing is apt to occur.

Further, if the heating is carried out to elevate the temperature satisfactorily so as not to cause defective brazing, the brazing temperature is elevated excessively for the radiator part, and thus inconveniently the filler material diffuses into the radiator tubes and the fins.

Further, in the oil cooler, since the brazed part is in contact with a refrigerant, local corrosion is apt to occur due to the potential difference between the brazed part and the core material part.

This problem cannot be solved by brazing by the conventional brazing technique.

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